JPS5924619B2 - battery charging device - Google Patents

Description

[Detailed description of the invention] The present invention relates to a battery charging device.

When a battery is used for photovoltaic power supply, the trickle charging current is 1/2 of the battery's rated capacity due to battery life.
It is set to 0 or less.

Therefore, for a battery with a rated capacity of, for example, 1800 mA, its trickle charging current must be 90 mA or less. However, current power sources, especially commercial AC power sources, are not always constant, so even with this fluctuation, the charging current must be kept at 1/20 or less of the above value. Conventionally, therefore, the source current is made sufficiently small in advance so that even the expected maximum fluctuation does not exceed 1/20, but for this purpose, it is natural that the charging current must be small. However, when the charging current is small, the discharge current cannot be increased when the battery is discharged (or the discharge time cannot be lengthened). , the purpose is to keep the charging current constant at all times, thereby charging the battery with a large charging current.

The present invention is characterized in that the charging current is compared with a fixed value by a comparator, the logical output of the comparison result is integrated, and the photoelectric current is maintained at a constant value by the integrated output. An embodiment of the present invention will be described with reference to the drawings. 1 is a terminal of an AC power supply, 2 is a transformer, 3 is a full-wave rectifier, and 4 is a terminal of an AC power supply.
is a battery to be charged, 5 is a charging resistor, 6 is a diode that prevents reverse discharge of battery 4, T is a transistor circuit that increases or decreases the charging current, and Darlington-connected transistor 8
, 9.

The voltage appearing across the photoresistor 5 is amplified by an amplifier 10 and further smoothed by a capacitor 11. The DC voltage E thus obtained is proportional to the photoelectric current flowing through the charging resistor 5. The voltage E is applied to a comparator 12. A reference voltage EK based on the Zener voltage of the Zener diode 13 is separately applied to the comparator 12 . Comparator 1
Two swords and others output logic output 1 when EK>E, and EK<
When E, a logic output of 0 is output. This output is capacitor 14
is integrated by an integrating circuit 15, and its integrated output is given to the base of transistor 8. If there is no comparator 12, transistor circuit T, etc., and if the charging current when the peak value of the AC voltage is the standard value is A in Figure 2, then as the peak value of the AC voltage increases, the charging current changes as shown in B, and as the peak value of the AC voltage decreases, the charging current changes as shown in C. As described above, when the charging current increases as indicated by B, this exceeds the trickle charging current determined from the battery capacity. In the configuration shown in the figure, assuming that the peak value of the AC voltage is the standard value, if the voltage E given to the comparator 12 based on the terminal voltage of the charging resistor 5 determined by the charging current at that time is greater than the reference voltage EK. Then, the logic output of the comparator 12 becomes 0, but because of the integration circuit 15, the base potential of the transistor 8 does not drop immediately, but gradually drops as time passes.

According to this decrease, the collector current of transistor 9,
In other words, the charging current also gradually decreases. According to this decrease, the voltage E decreases and becomes lower than the reference voltage Ek, and the logic output of the comparator 12 becomes 1. However, because of the integration circuit 15, the base potential of the transistor 8 does not increase immediately, but increases over time. Due to this increase, the collector current of transistor 9, that is, the charging current also increases. Repeat this below. If the discharge time constant of the integrating circuit 15 is longer than the half-wave cycle of the AC voltage, then
The waveform of the charging current at this time is as shown in A of FIG. Now suppose that the peak value becomes higher due to fluctuations in the AC voltage.

At this time as well, the base potential of the transistor 8 fluctuates by comparing the voltage E and the reference voltage EK, but the reference voltage Ek
Since there is no difference from the case described above, the collector current of transistor 9, that is, the photoelectric current is the same. In reality, since the peak value of the AC voltage has become high, the tail of the current waveform becomes wider, so if the charging current is the same, it will look like the charging current waveform shown in B in Figure 3. The peak value is lower than that of waveform A so that it has the same area as waveform A. Conversely, even when the peak value decreases due to fluctuations in the father current voltage, the collector current of transistor 9 remains the same, and the photoelectric current waveform in this case has the same area as waveform A, as shown in Figure 3C. The peak value becomes higher so that they remain the same. Here, if the integrator circuit 15 is
And. For example, when the logic output of the comparator 12 becomes O because the voltage E becomes larger than the reference voltage Ek, the base potential of the transistor 8 immediately decreases, and the transistor 8 is suddenly cut off, so that no charging current flows. Put it away.

In other words, this causes the charging current to be repeatedly interrupted. In order to secure a predetermined value for the discharging current of a battery, it is necessary to supply the necessary amount of charging current, but if the charging current is intermittent as described above, there will be a period during which no charging current flows. By the occurrence of
If this continues, it will not be possible to secure the amount of current required as the charging current. In order to secure this necessary amount of current, it is necessary to supply a charging current with a current waveform with a high peak value, but if such a charging current with a high peak value is supplied, the battery electrode becomes damaged. However, if the integrating circuit 15 is provided, the comparator 12
Even when the logic output of the transistor 8 becomes O, the base potential of the transistor 8 does not immediately decrease, but gradually decreases. Since the voltage E decreases until the transistor 8 is finally turned off, the logic output of the comparator 12 becomes 1, and the base potential of the transistor 8 increases. In this way,
Since the transistor 8 is never turned off, the charging current increases and decreases without being interrupted. Therefore, it is not necessary to flow a current with a high peak value as a charging current, so that there is no possibility of damaging the battery electrodes. As described in detail above, according to the present invention, when rectifying AC voltage to charge a battery, the photoelectric current can be kept constant even if the AC voltage fluctuates, so that voltage fluctuations can be avoided as in the conventional case. It is no longer necessary to reduce the charging current in advance in anticipation of this, and the effect is that the discharge current of the battery can be increased.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a waveform diagram of a charging current in a conventional configuration, and FIG. 3 is a waveform diagram of a charging current according to the present invention. 1... AC power supply terminal, 3... Full wave rectifier, 4... Battery, 5... Charging resistor,
7...Transistor circuit, 10...Amplifier, 12...Comparator, 13...Zena diode, 15...Integrator circuit .

Claims (1)

[Claims] 1. A battery charging device that full-wave rectifies an alternating current voltage and supplies charging current to the battery, including a comparator that compares a voltage proportional to the charging current with a reference voltage, and an integrating circuit that integrates the logic output of the comparator. and a transistor circuit that controls the charging current so as to keep it constant based on the integral output of the integrating circuit.